Also use static rules when user has not enabled DNS rules

#285

app/src/main/java/com/frostnerd/smokescreen/service/DnsVpnService.kt

@@ -1585,11 +1585,11 @@ class DnsVpnService : VpnService(), Runnable, CoroutineScope {
         return dnsCache
     }
 
-    private fun createLocalResolver(): LocalResolver? {
+    private fun createLocalResolver(): LocalResolver {
         return if (getPreferences().dnsRulesEnabled) {
             DnsRuleResolver(applicationContext)
         } else {
-            null
+            StaticDnsRuleResolver()
         }
     }
 

app/src/main/java/com/frostnerd/smokescreen/util/proxy/DnsRuleResolver.kt

@@ -42,10 +42,6 @@ class DnsRuleResolver(context: Context) : LocalResolver(false) {
     private var cachedWildcardResolved = MaxSizeMap<Int, String>(maxWildcardResolvedCacheSize, 30)
     private var cachedNonIncluded = HashSet<Int>(15)
 
-    private val staticRules = mapOf<String, List<Record<*>>>(
-        "use-application-dns.net" to emptyList()
-    )
-
     private var previousRefreshJob:Job? = null
 
     init {
@@ -204,7 +200,7 @@ class DnsRuleResolver(context: Context) : LocalResolver(false) {
     }
 
     override fun canResolve(question: Question): Boolean {
-        if(staticRules.containsKey(question.name?.toString()?.lowercase())) {
+        if(StaticDnsRuleResolver.staticRules.containsKey(question.name?.toString()?.lowercase())) {
             return true
         }
         return if ((ruleCount == 0 || (ruleCount != null && ruleCount == whitelistCount)) || (question.type != Record.TYPE.A && question.type != Record.TYPE.AAAA)) {
@@ -230,8 +226,8 @@ class DnsRuleResolver(context: Context) : LocalResolver(false) {
     }
 
     override fun resolve(question: Question): List<Record<*>> {
-        if(staticRules.containsKey(question.name?.toString()?.lowercase())) {
-            return staticRules[question.name?.toString()?.lowercase()]!!
+        if(StaticDnsRuleResolver.staticRules.containsKey(question.name?.toString()?.lowercase())) {
+            return StaticDnsRuleResolver.staticRules[question.name?.toString()?.lowercase()] ?: emptyList()
         }
         val result = resolveResults.remove(question.hashCode())
         return result?.let {

app/src/main/java/com/frostnerd/smokescreen/util/proxy/StaticDnsRuleResolver.kt

+package com.frostnerd.smokescreen.util.proxy
+
+import com.frostnerd.dnstunnelproxy.LocalResolver
+import org.minidns.dnsmessage.DnsMessage
+import org.minidns.dnsmessage.Question
+import org.minidns.record.*
+
+// Resolver which does not use user rules.
+class StaticDnsRuleResolver : LocalResolver(false) {
+    companion object {
+        val staticRules = mapOf<String, List<Record<*>>>(
+            "use-application-dns.net" to emptyList()
+        )
+    }
+
+    override fun canResolve(question: Question): Boolean {
+        return staticRules.containsKey(question.name?.toString()?.lowercase())
+    }
+
+    override fun resolve(question: Question): List<Record<*>> {
+        return staticRules[question.name?.toString()?.lowercase()] ?: emptyList()
+    }
+
+    override fun cleanup() {
+
+    }
+
+    override fun mapResponse(message: DnsMessage): DnsMessage {
+        return message
+    }
+}
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